The effect of varying dietary energy on gonad development at first sexual maturity of the Sharptooth catfish (Clarias gariepinus Burchell, 1822)

摘要

The objective of this study was to investigate the effects of five isonitrogenous (35% crude protein) diets having different energy contents; 10.85, 11.82, 12.73, 13.69, and 15.06 MJ DE/kg, respectively, on the gonad development and weight gain of Sharptooth catfish fingerlings. Energy contents of the experimental diets were increased with the increasing amount of soy-acid oil (0, 4, 8.5, 13, 18%) and each group of fish was fed on their respective diets (group I was fed diet I) during 180 days. The gonad maturation was significantly affected by dietary energy. In both sexes, the histological inspections of the gonads did reveal differences among the fish fed different energetic diets. Fish fed diets I, II, and III had significantly heavier and more developed gonads compared to those on diets IV and V. Fish fed the higher energetic diets (IV and V) had partially low numbers of yolky oocytes compared to other groups. The mean GSI values of female and male fish fed with diet III was significantly greater than those fed diets with higher dietary energy; however, higher HSI values were recorded for fish fed with the higher energetic diets (IV and V). Also, the best weight gain for both males and females were recorded from the fish fed diet III (12.73 MJ DE/kg). Therefore, on the basis of the present results, among energy levels tested, 12.73 MJ DE/kg was found to be optimal for healthy gonad development and weight gain.